Senior executives at some of the biggest exchanges in the US have given their initial reactions to the two mergers in their industry announced this week, and have played down the potential impact they will have on competition.

On Wednesday this week the London Stock Exchange and the Toronto Stock Exchange revealed plans to merge and this was closely followed by arch rivals Deutsche Börse and NYSE Euronext confirming they intended to do the same.

At the Credit Suisse Financial Services Conference in New York yesterday, senior executives from two of the US's biggest stock markets gave their reaction to the week's events.

Adena Friedman, chief financial officer of Nasdaq OMX, said: “The last 48 hours have been a whirlwind and the best thing for us and our shareholders is to be analytical and rational when looking at all potential outcomes.”

She added that both deals had huge regulatory implications and that it would take a long time before Nasdaq OMX and its competitors knew how the merged groups would shape their industry. Canadian Industry Minister Tony Clement said yesterday that he hoped to announce next week whether there will a government review of the merger between the LSE and TMX Group.

Freidman said: “The deals do not provide a significant competitive dynamic to what we are trying to do and there may be opportunities from a shift in share in options or in Europe. Our job is to sit back and fully understand these deals as a fiduciary for our shareholders.”

Jamie Parisi, chief financial officer of CME Group, said: “The combination of cash markets is what it is and won’t significantly change our competitive competition. In derivatives both Deutsche Börse and NYSE Euronext are good competitors and will remain so if they are put together. However we have done a really good job at competing in Europe and we will continue to do so.”

During the CME's results call earlier this month, chief executive Craig Donohue said that about 20 firms are in talks to join as members or users of CME Clearing Europe, a new UK clearing house, that has received regulatory approval.

NYSE Euronext was due to present at the same conference but cancelled its participation yesterday.

William Brodsky, chief executive of CBOE Holdings, did not see believe there would be an impact on the US options market. He said on a results call yesterday: “I don't think anything we saw or talked about going on Wednesday is going to change competition in a meaningful way.”

Meanwhile, Michael Bloomberg, mayor of New York City, came out in support of the Deutsche Börse deal with NYSE Euronext. According to Dow Jones, Bloomberg said in a news conference: “This is good for American companies that want to compete around the world. If the New York Stock Exchange didn't form a partnership like this, they could be frozen out.”